The aim of this program project proposal is to pursue research in basic and clinical aspects of neurophysiology and neuropsychology relevant to an increased understanding of mental retardation and related aspects of human development. This aim will be implemented by utilizing the talents of a group of basic and clinical researchers in a cooperative and collaborative manner. Members of this group will undertake the following tasks: 1. studies in animals designed to elucidate aspects of the neural bases of development of behavior in infants and of such "plastic" processes as learning, performance and attention in adult animals. 2. the investigation of cellular bases of the phenomena included in 1) above by analyzing neuronal membrane activity and action potential production in pertinent neural systems in whole animals and by the identification of model mammalian neural sub-systems which show electrophysiological response plasticity. 3. the provision of a milieu for attracting and training of young scientists in these research areas.